The staphylococci in general, and S. aureus in particular, are the most prominent bacterial pathogens causing musculoskeletal infection. These infections are remarkably difficult to treat. This is due to a number of factors including the failure to detect the infection until it has progressed to a chronic infection characterized by formation of necrotic bone, the continued emergence of antibiotic resistance among the staphylococci, which are the preeminent musculoskeletal pathogens, and the inability to deliver effective concentrations of the most appropriate antibiotic to the site of infection. These three issues are the experimental focus of this proposal. Specifically, the aims of this proposal are: Aim 1: To optimize FDG-PET for the early detection of musculoskeletal infection. This aim is based on our belief that we can increase the specificity of FDG-PET without an unacceptable sacrifice of sensitivity by optimizing methods of data acquisition and analysis in the specific context of musculoskeletal infection vs. other forms of inflammation. We will evaluate this hypothesis using an established rabbit model of postsurgical osteomyelitis. Aim 2: To develop a rapid diagnostic method that will facilitate determinative antimicrobial therapy of staphylococcal musculoskeletal infection. We will build on previous experiments in the Pi's laboratory to develop PCR-based methods that address the most critical therapeutic issues and can be used for the direct analysis of clinical samples without the need for cultural amplification. Aim 3: To optimize antibiotic therapy for biofilm-associated musculoskeletal infection. We will use our rabbit osteomyelitis model to determine the optimal method of delivering the most commonly used anti-staphylococcal agents directly to the site of infection. We will also evaluate the utility of FDG-PET as a means of monitoring the response to antimicrobial therapy. Lay description: Staphylococcus aureus is the most common pathogen causing devastating bone and joint infection. These infections are very difficult to treat and often require surgery or even amputation. The goals of our work are to enhance the detection, diagnosis and treatment of these infections. While the experiments we propose will focus on S. aureus, the results will be applicable to other bacterial pathogens that cause musculoskeletal infection. The results will also be applicable to patient care in that they will ultimately form the basis for clinical recommendations regarding these critical diagnostic and treatment issues. This is consistent with the NIH Roadmap emphasis on "bench-to-bedside" translational research.